: Dear Sir,: I have been told the real problem with US toilets is not the flush volume it is the smaller outflow and possibly tighter turn, that the material has to fit thru. Is this the real problem? If so is there a solution? Thank you, Bob

Bob,It is more than that. Speed of water plays a part. As does smooth rounded trapway bends. Some toilets have rough edges at the exit of the trapway. The better 1.6 toilets need plunging less than the old 5.0 toilets, and quite a bit less than many of the 3.5 toilets. A performance toilet will have speed, smooth bends, consistently round trapway, with no catching edges. Two inches-plus or minus works fine.